Manufacture of adiponitrile



United States Patent 3,424,784 MANUFACTURE OF ADIPONITRILE George Barslry, 50 E. 41st St., New York, N.Y. 10017 No Drawing. Filed July 14, 1965, Ser. No. 472,025 U.S. Cl. 260-4653 3 Claims Int. Cl. Cil7c 121/02, 121/26 ABSTRACT OF THE DISCLOSURE A process for producing adiponitrile which comprises mixing thiodipropionitrile with a metal whch forms sulfides with thio-dipropionitrile, heating said mixture to a temperature of about 175 C., said heating being continued for about 4 hours.

This invention is for a process for making adiponitrile which is an important intermediate in the manufacture of nylon.

One of the present processes for the manufacture of adiponitrile consists in ammoniation of adipic acid. The adipic acid is produced by oxidaton of cyclohexane. An improved process for adiponitrlie was developed by du- Pont starting from butadiene, chlorinating, treating with cyanide and then hydrogenating. Both these processes are quite complicated and costly.

Acrylonitrile is a cheap material and has attracted attention as a possible raw material for adiponitrile. The reaction can be considered as a reductive coupling, as is indicated by the following equation:

It has been proposed to heat acrylonitrile under pressure with magnesium turnings and alcohol but the yields are very low. It has also been proposed to carry out the reductive coupling by electrolysis. This is an expensive process because of the amount of power consumed, the expensive electrolyte required and the high cost and low capacity of electrolytic cells.

In my process, acrylonitrile is first reacted with hydrogen sulfide to form thio-dipropionitrile:

This reaction goes easily and is well described in the literature. Hydrogen sulfide is a cheap reagent and can be made by heating heavy petroleum with elemental sulfur.

The second step of my process may be called coupling desulfurization. I heat thiodipropionitrile with finely divided metal such as cement copper and bring about the reaction:

The following example is illustrative of my process: 140 parts of dry thiodipropionitrile are heated with 3,424,784 Patented Jan. 28, 1969 parts of metallic copper powder relatively free from oxide with good agitation in a nitrogen atmosphere. The temperature is maintained at 175 C. for four hours. The mixture turns black. After cooling, the copper sulfide and metallic copper remaining are filtered off and washed with alcohol. The alcohol wash liquor is added to the crude filtrate. This is then heated to remove the alcohol which is recovered for reuse. The crude adiponitrile is purified by vacuum distillation through a column to collect adiponitrile at -l68 C. at about 15 mm. of mercury. Unreacted thiodipropionitrile remains in the residue. It can, of course, be added to the next batch. It is preferable in repeated runs to remove a part of the residue and periodically vacuum distill it to get rid of accumulated impurities.

The copper sulfide formed as the coproduct in my process is valuable as it can be sold for its copper content, thus reducing very greatly the raw material costs of the process.

While I have described the use of metallic copper in the example above, other metals that form sulfides readily may 'be used, particularly the heavy metals. Such metals as nickel, silver, mercury, cadmium, cobalt, iron, or zinc may be substituted for copper with like results.

Yields in coupling desulfurization reaction are improved by keeping moisture and oxygen away from the reacting mass.

I do not try to completely convert the thiodipropionitrile in each batch but prefer to have an excess which serves as a solvent and also speeds up reaction. Since I reuse the excess, there is no overall loss in yield.

I claim:

1. A process for producing adiponitrile which comprises mixing thiodipropionitrile with copper, heating said mixture to a temperature of C., said heating being continued for about 4 hours to convert said thiodipropionitrile into adiponitrile by desulfurization thereof, said copper being present in an amount of about 1 part to 1.4 parts of said thiodipropionitrile.

2. A process according to claim 1 wherein said sulfide is recovered.

3. A process according to claim 1 wherein oxygen and moisture are absent.

References Cited UNITED STATES PATENTS 3,185,743 5/1965 La Combe 260-4659 JOSEPH P. BRUST, Primary Examiner.

US. Cl. X.R. 

